Low water cutoff



Feb. 25, 1941.

o; F. cA LsoN LOW WATER CUTOFF Filed Sept. 6, 1958 Sheets-Sheet 1 570672237 Uxarf? Carbon Febo 1941 o. F: CARLSON ,996

LOW WATER CUTOFF I Filed Sept. 6, 19558 3 Sheets-Sheet 2 we 0/ 0L 5 59- 441/ w w w /05 4- Feb, 25,, m1. 0. F. CARLSON 3 3 6 LOW WATER CUTOFF Filed Sept. 6, 19358 3 Sheets-Sheet 5 Patented Feb. 25 1941 UNITED STATES PATENT OFFIC LOW WATER CUTOFF Application September 6, 1938, Serial No. 228,566

3 Claims.

This invention relates generally to control devices for boilers and the like and is more particularly concerned with control devices that respond to liquid level for controlling water feeders, burners, fuel supply, and the like.

The object and general nature of this invention resides in the provision of a low water outoff that is responsive to the liquid level in the boiler and may be employed for controlling a water feeder for maintaining substantially constant water level in the boiler and also shutting down the burner if the liquid level falls too low. More specifically, it is a feature of this invention to provide a float and float chamber with a switch assembly which includes two units, both controlled by the float and one acting to control the water feeder while the other is arranged to control the burner.

Another feature of this invention resides in the provision of a float chamber which is formed, at least partially, by a sleeve or similar part that threads directly into the boiler at the water level thereof and does not require any other connections to the boiler for its installation. Another feature of this invention is an improved form of screen for the float chamber.

These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description, taken in conjunction with the accompanying drawings.

- In the drawings:

Figure 1 is a longitudinal vertical section taken through a boiler control device embodying the principles of the present invention;

Figure 2 is an elevation of the switch assembly as it appears when detached from the float chamber and the outer switch housing, corresponding generally to a View along the line 2-2 of Figure l;

Figure 3 is an end view taken generally along Figure 9 is a perspective view of one of the four screen sections which make up a screen at the inner end of the float chamber;

Figure 10 is a view of the screen disc that holds the screen sections of Figure 9 in position;

Figure 11 is a fragmentary view showing the manner of inserting each of the four screen sections;

Figure 12 is a perspective view of one of the two brackets securing the switch unit to the float chamber; and

Figures 13 and 14 show a modified form of float chamber and screen.

Referring now to the drawings, particularly to Figure 1, the boiler or other device on which the control unit is mounted is indicated in its entirety by the reference numeral l and includes a wall 2 having a screw threaded opening 3 formed therein substantially at the water level, indicated at 4, of the boiler. The control device in which the principles of the present invention have been embodied is indicated in its entirety by the reference numeral 6, and consists generally of a float chamber in which the float is movably disposed and a switch assembly or other controlling device mounted thereon.

The float chamber in indicated at l and consists of a casing 8 and a sleeve 9 rotatable with respect to the casing 8. The latter is disposed generally vertically and has an upper threaded opening l0 closed by a plug II and a lower closure plate l2 fastened by cap screws l3 or the like. The plate l2 has a threaded opening M which may be closed by a plug I5. It will be noted that the lower portion of the casing 8 extends below the sleeve 9 so that there is little likelihood of any sediment or other deposits collecting in the sleeve. The plug l4 may be removed to drain the casing 8, but if desired the entire plate I2 may be removed. The casing 8 is also provided with a recess I6 which receives the flange I 1 that is formed on the outer end of the sleeve 9. The inner end of the latter is threaded as at l8 and is adapted to be screwed into the opening 3 of the boiler wall in leaktight relation. A gasket I9 is disposed between the flange I! on the sleeve 9 and the socket or recess l6 of the casing 8. A clamping ring 2| is disposed about the sleeve 9 and bears against the flange l'l thereof to holdthe same firmly to the casing 8. The clamping ring 2| is tightened by any suitable means, such as clamping screws 22 extending through a flange 23 on the casing 8 surrounding the socket l6 and threaded into the clamping ring 2|.

When the clamping ring 2| is loosened, the sleeve 9 may be turned with respect to the easing 8, thereby facilitating screwing the sleeve into the boiler 2. The sleeve 9 has a polygonal wrench receiving section 25, and the inner end of the sleeve 9 is reduced, as at 21, and provided with openings 21a to receive a screen which is indicated in its entirety by the reference nu meral 28 and which preferably extends into the boiler, as indicated. The screen 28 comprises four sections 28a, each of which is provided with an inwardly bent tongue 29 and projecting lugs 29a, as best shown in Figure 9. Also, each screen section 280. includes a pair of slots 30 formed in the end of screen section 280. opposite the tongue 29, and one or more openings 30a. The screen 28 also includes a circular disc 3| provided with slots 3|a and pairs of tongues 32, as best shown in Figure 10. The screen 28 is capable of being assembled easily and quickly on the inner end 21 of the sleeve 9 in the manner indicated in Figure 11. That is, each of the four screen sections 28a is individually mounted by inserting the tongue 29 into the associated sleeve opening 210. with the screen section 28a in the position shown in Figure 11 so that the end portion of the tongue 29 engages underneath one edge of the opening 21a, as best shown in Figure 1, when the screen section 28 is swung into the position shown in Figure 1. The disc 3| with the pairs of tongues 32 is held in position by engaging the tongues of each pair into the adjacent slots 30 of the four screen sections 28a, and then bending over the tongues 32, thus holding the four screen sections 28a in cylindrical relation and also holding the screen end 3| in place. The openings 38a and 3|a provide for a free flow of water between the boiler and the float chamber 1.

A float 33 is movably mounted within the float chamber 1 and is of the tubular elongated type.

At its inner end the float 33 extends through the sleeve 9 and partially into the space within the screen 28, and at its outer end the float 33 carries a float arm 35 which is secured to the head of the float in any suitable manner, as by a screw 36 that extends through the head of the float, indicated at 31, and into a tapped opening in the inner end of the float arm 35. The head or cap 31 of the float is secured to the main body thereof in any suitable manner, as by soldering or the like.

One end of the casing 8 is open, as at 45, and receives an end plate 4| which is clamped to the casing 8 by a clamping ring 42, generally U- shaped in section having inner and outer flanges 42a and 42b, and a plurality of cap screws 43. The central portion of the end plate 4| is cupped, as at 44, and receives a ring 45 having a central opening 46 and provided with a pair of lugs or ears 41. A pivot pin 48 is carried by the ears 41 and, in turn, extends through an opening in the float arm 35 and supports the float 33 for pivotal movement in the float chamber 1. The supporting ring 45 is secured in any suitable manner, as by soldering or the like, to the cupped section 44 of the end plate 4|, the latter having a central opening registering with the opening 46 in the ring 45.

The outer end of the float arm extends through the openings 46 and 5| and into the space beyond the end plate 4|, and in order to provide a seal between the float 33 and the float chamber a bellows 53 is disposed about the float arm 35 and its supporting lugs 41. The inner end of the bellows 53 is disposed between a washer 55 and the end of the float arm 35, whereby when the attaching screw 36 is tightened the bellows is secured to the outer end of the float 33. The outer end of the bellows 53 is secured by soldering or otherwise to the ring 45 and the end plate 4i. Thus, one end of the bellows 53 is sealed to the float chamber and the other end to the float 33, whereby the latter may move vertically in response to changes in the water level in the boiler with considerable freedom of movement about the pivot pin 48.

The switch assembly that is controlled by the float 33 is indicated in its entirety by the reference numeral 80 and is disposed within and carried by a shell 6|, one wall of which is open, at 52, and the other end of the shell 5| receives the channel ring 42 which clamps the plate 4| to the float chamber. The switch assembly 50 includes a casing 65 that is formed by a base member 55 and a cover 61, both being formed of insulating material, as best shown in Figures 4, 5 and 6. The base 68 includes at one side thereof a raised portion 68 around which the edge of the cover 51 fits, and the opposite side of the base 65 is also provided with a raised section 69 which is recessed at 1| to receive terminals referred to below. The cover 51 of the switch casing 65 is provided with an elongated boss 13 which is apertured, as at 14 and and recessed, as at 11, forming two upstanding side walls 18. The base 66 and the cover 61 are made of insulating material, and a pair of screws 19 pass upwardly through the base and are threaded into tapped openings in bosses 80 formed on the cover 61 to secure the cover and base together.

A pivot pin 81 is disposed in suitable openings in the recess walls 18, and a lever 82 has a portion disposed within the recess 11 and pivotally mounted on the pin 8|. The lever 82 has a recess 83 and lateral arm sections 84 disposed generally in the plane of the boss 13. A pair of arms 81 and 88 are also pivotally mounted on. the pin 8| and formed to lie alongside the sections 84 of the lever 82. Each of the arms 81 and 88 is provided with a laterally extended lug 89 disposed over the bores 14 and 15 formed in the cover 61. Plungers 9i and 92 are disposed in said bores and are engaged by the lugs 89 on the arms 81 and 88.

Each of the arms 81 and 88 may be fixed in adjusted position relative to the lever 82 independently of the other arm. Each adjusting means includes a cam screw 94 which is best shown in Figure '7. Each cam screw 94 includes a head 95 and a threaded shank 95 formed integrally with and arranged in eccentric relation with respect to the head 95. The lever 82 is provided with two screw threaded openings receiving the cam screws 94, and each cam screw carries a lock nut 91. The head 95 of each of the cam screws is generally cylindrical and is received within an elongated slot 98 formed in each of the arms 81 and 88. Thus, when the lock nut 91 of either cam screw is loosened, the screw may be turned, and due to the eccentric relation between the shank and the head of the screw, turning the screw 95 adjusts the position of the arm relative to the lever. After the arm is adjusted, the lock nut 91 may be tightened to retain the desired adjustment. It will be noted that adjustment of either of the arms 81 and 88 takes place about the pivot 8|, which is a pivot about which the lever 82 swings, and that each adjustment is independent of the other.

The lever 82' is adapted to be actuated by the extended end of the float arm 35. The float arm carries a pivot IEI upon which a roller I02 is pivoted, and when the switch mechanism 60 is in place, the recess 83 of the lever 82 is disposed on opposite sides of the roller I02, as best shown in Figure 1, whereby vertical swinging movement of the float 33 will swing the lever 82 in one direction or the other, and swinging movement of the lever 82 depresses one or the other of the plungers 9I and 92. The switch units controlled by the plungers 9| and 92 will now be described.

As best shown in Figure 6, the housing 65 encloses two separate switch units I05 and I06 which are arranged along side one another but in opposite relation and generally transverse with respect to the plane of the operating lever 82 which controls both of the switch units. The switch units I05 and I06 are substantially identical so that a description of one will suffice, corresponding parts of the two units being indicated by the same reference numerals.

Referring now to Figure 4, the base 66 carries a stationary terminal I I0 that includes a sleeve I I I to which the horizontal portion I I2 of a bracket H3 is riveted or otherwise fixed in a suitable manner. The sleeve II I is threaded to receive a screw I I4 under the head of which a flanged terminal washer H6 is disposed. Each washer has one or more notches I I1 to accommodate the wire or conductor that is fastened by the screw I I4 to the terminal I I0. The base 66 also carries a stationary contact structure I20 which'comprises a sleeve I2I internally threaded to receive a terminal screw I22 substantially identical with the screw I I4 described above. Underneath the head of the screw I22 is a flanged terminal washer I23 having a conductor receiving recess I24. The sleeve I2I carries an apertured head I26 in which a contact element I21 is fixed, as by being riveted therein. Underneath the'head I26 of the sleeve I2I is a plate I 28 having an end I29 extending 5 over the intermediate portion of the small horseshoe magnet I3! the latter being seated in a recess I32 formed in the base 66 to receive it. The two poles of the magnet I3I are indicated at I33 and I34 (Figure 5). The magnet I3I influences a movable switch element which will now be described.

The bracket II3, which is fixed to the base by the terminal II I, includes a standard section I38 which is apertured to receive a screw I39 which is threaded into a clip MI and secures the upwardly bent end I42 of a spring arm I43. The opposite end of the spring arm I43 carries a contact element I45 which has a shank I46 extending through an aperture in the spring arm I 43 and through an aperture in an armature I41. The outer end of the latter has a tongue I48 bent over the outer end of the spring arm I43 to secure the firm attachment of the armature I41 to the outer end of the spring arm I43. As best shown in Figure 8, portions I49 of the armature are pressed into openings I50 in the arm I43, thereby preventing any relative movement between the arm and the armature.

The armature I41 is disposed, as best shown in Figure 4, directly above the magnet I3I, close enough to the magnet I3I so that when the contacts I21 and I45 are in engagement the magnet exerts an appreciable pull on the armature to hold the contacts in engagement until a force is exerted through the spring arm I43 that is sufiicient to overcome the pull of the magnet, whereupon the contacts I21 and I45 separate with a quick or snap action. The movement of the outer end of the spring arm I 43 is limited by its contact with the abutment portion 61a formed on the casing cover 61.

The means acting through the spring arm I43 to separate the contacts consists of a lever I5I which is generally U-shaped in section and has an extended portion I52 engaged by the head of the associated plunger 9I or 92'. The sides of the member I5I are extended in the form of arms I54 and I55 and receive a pivot pin I56 which is supported in a pair of ears I51 and I58 which extend upwardly from and form a part of the bracket H3. The spring arm I43 passes between the arm sections I54 and I55, and the ends of the arm sections I54 and I55 are apertured to rotatably receive the reduced ends of a roller I60 that lies underneath the spring arm I43 adjacent the point where the latter is anchored to the standard I38.

The boss or raised portion 68 on the base 66 and the cover 51 are preferably rectangular in formation, thereby facilitating a proper assembly of the switch mechanism and insuring that the plungers 9I and 92 will be in the proper position relative to their operating levers I5I and the abutment stops 61a for the spring arms, regardless as to which way the cover is applied to the base.

The shell 6| carries an extension I65 having an aperture I66 therein and the extension I65 extends from one edge of the opening 62. The opening 62 is closed by a terminal cover I61 which encloses the exposed face of the switch assembly 60 and has a flanged portion I68. The portion I68 has an aperture I69 which receives a screw I1I by which the cover I61 is attached to the shell 6I. The shell 6I has a tapped opening I12 to receive the screw I1 I The switch assembly 60 is secured to the float chamber by a pair of brackets I15, best shown in Figures 1, 2, 3, and 12. Each bracket consists of a generally U-shaped strap member having an intermediate section I11, fastened to the base 66 by a pair of screws I18, and a pair of arms I19 which extending along the switch case 65 (Figure l) and terminate in outwardly bent arcuate portions I8I which are arranged to fit between the flanges 42a and 42b of the clamping ring 42 and are apertured, as at I82 (Figure 2), to receive screws I83 (Figure 3) which are threaded into tapped openings in the clamping ring 42 and by which the brackets are fixed to the float chamber to hold the actuating lever 82 in operative relation with the roller I02 at the outer end of the fioat arm 35. The outer portion or flange of the base 66 is provided with a pair of apertures I84 (Figure 2) to receive a pair of screws I85 (Figure 3) by which the shell 6| is fastened in place about the switch assembly 60. The screws I85 may thread into the base 66 or may extend to and thread into the ring 42. The conductors (not shown) from the switch terminals- H0 and I20 extend outwardly through the openings I66 to the units to be controlled, and to simplify the connections the terminal IIO (Figure 3) of theswitch unit I06 may be connected by a copper strip I86 to the terminal I20 of the other switch unit I05.

Preferably the shell 6| may be secured in any one of four positions so as tolead the conductors in the desired direction. To this end the base 66 has recesses or holes I81 (Figures 2 and 3) and the intermediate sections I" of the brackets I15 have holes I88 (Figure 2) to receive the attaching screws I when the shell BI is turned from the position shown. The shell BI may, of course, be turned 180 by using the holes I84 in the base 65.

In operation, as the float 33 rises and falls in response to variations in the water level in the boiler I, the outer end of the float arm 35 swings the actuating lever 82 about its pivot 8|. The movement of the lever 82 acts through the arm sections 81 and 88 to actuate one or the other of the plungers SI and 92, the heads of which engage the lateral arm sections 89. For example, if the liquid level in the boiler I falls the downward movement of the float 33 swings the float arm 35 in a counterclockwise direction (Figure 1) about the pivot 48, which swings the actuating lever 8.! in a clockwise direction about its pivot 8| on the switch housing 65. This movement of the lever 82 depresses the plunger 92 and swings the lever I5I about its pivot support I56 (Figure 4), which is in a clockwise direction, and causes the roller I60 to bear upwardly against the spring arm I43 adjacent its inner or anchored end. It will be remembered, however, that the magnet I3I exerts a pull on the armature I l'i to hold the contacts I21 and I45 in engagement with a certain amount of force, so that the movement of the roller I60 against the spring arm I43 flexes the latter until the spring arm exerts a force that is suflicient to overcome the pull of the magnet I3l. As soon as the force of the latter is overcome, the armature is pulled away from the magnet and the spring arm I43 separates the contacts I21 and I45 very quickly and with a snap action.

When the liquid level in the boiler I rises, the upward movement of the float 33 swings the lever 82 in the other direction, counterclockwise as viewed in Figures 1 and 5, which first relaxes the pressure against the plunger 92, permitting the resilience of the spring I43 to bring the contacts I45 and I2! of the switch unit I05 into engagement, and then the other plunger 9| of the other switch Lmit I06 will be depressed, snapping the contacts I21 and I45 of that unit into open position.

The two switch units I05 and I06, controlled by the float 33, may be connected to any suitable controlling devices. By way of example, the switch unit I06 may be connected to control a water feeder, the switch unit I06 being closed when the float 33 is in the lower position and opened when the float is in an upper position. Thus, the closing of the switch unit I06 may be employed for directing feed water into the boiler until the level therein rises sufficient to raise the float and open the switch I06. The other switch unit I05 may be arranged to control the burner for the boiler I and, according to the present invention, is preferably arranged so that when the float 33 falls to an exceptionally low level in the boiler, the switch unit I05 will be opened, thereby shutting off the burner, as by shutting oif the fuel supply, or otherwise controlling the same. By the adjustment of the arms 81 and 88 through the adjusting screws 94, each of the switch units may be arranged for actuation at the float position desired in order to secure the' required relation between the devices controlled by the switch units I05 and I00. As described, where the two units are a water feeder and a low water cutoif for the burner, the switch controlling the water feeder is so arranged that normally the level 4 in the boiler is maintained above the position at which the switch unit I05 is opened to shut off the burner as a safety measure. In other words, the parts are so adjusted that the float 33 rises and falls to open and close the water feeder switch unit I06 without opening the cutoff switch unit I05, but if the liquid level 4 in the boiler I should fall to some predetermined excessively low position, then the switch unit I05 will be opened and shut off the burner.

The present invention is, of course, not limited to the use of a water feeder and burner cutoff, although that is the preferred arrangement. The switch units I05 and I06 may be connected to control any device desired. Further, if it should be desired to provide a pressure responsive unit, the plug II ma be removed and a pressure sensitive device, such as the one shown in my copending application, Serial No. 163,433, now Patent No. 2,220,144, issued November 5, 1940, installed in the opening I0 so that the plunger of the device will also control the position of the float 33.

The modified form of float chamber and screen construction shown in Figures 13 and 14 includes a float chamber 9a having a somewhat longer neck portion I9I- than the sleeve 9 shown in Figure 1. In Figure 13, the portion I9I is threaded, as at I92, so as to be screwed into a boiler wall 2. The end section I93 of the sleeve 9a is provided with openings I94, like the openings Bid at the inner end of the sleeve 9 of Figure 1. The inner end of the sleeve I9I is closed by a screen disc I95 having a flange I96 adapted to closely embrace the inner end I93 of the sleeve 9a and a plurality of openings I9! and I98, the latter being formed by portions I98a (Figure 13) which are pressed out of the plane of the disc at I95. The flange I95 is provided with four tongues I09, each of which is formed by slitting the flange and bending the stock out of the plane of the flange. One of the tongues, the lower one as indicated at Figure 14, is bent inwardly, while the other tongues are bent outwardly, and the screen 595 is assembled by inserting the lower tongue into the opening I94 (Figure 13), thus locating the screen I95 in position so that the remaining three tongues I99 can be struck a blow and bent downwardly into the otheropenings I94, thereby securing the screen in position. As best indicated in Figure 13, the lengthening of the float chamber 39a. disposes the o erating parts at a somewhat greater distance from the boiler I, and hence the float 33 is disposed at its inner end wholly within the sleeve rm, and does not project therefrom as in Figure 1. However, in cases where the float 33 is shorter than indicated in Figure l, the screen I95 may be employed for the construction shown in Fig ure 1, instead of the screen 28, if desired.

While I have shown and described above the preferred structure in which the principles of the present invention have been embodied, it is to be understood that my invention is not to be limited to the specific details shown and described above, but that, in fact, widely different means ma be employed in the practice of the broader aspects of my invention.

What I claim, therefore, and desire to secure by Letters Patent is:

1. A low water cutofi for boilers and the like comprising .a float chamber having a sleeve section at one end, said boiler having an opening to receive said sleeve section of the float chamber, a float mounted in said chamber and having its inner end extendin into said sleeve section and through the opening in said boiler, the inner end of said sleeve section being apertured, and .a screen for the inner end of said sleeve section, comprising a plurality of screen sections, each having a tongue adapted to be inserted in the corresponding opening in said sleeve section and a closure disc having a tongue and slot connection with said screen sections for holding the latter in assembled relation.

2. In a low water cutoff, a float chamber, a float therein having a float arm sealingly connected to and extending outwardly of said chamber, and an operating unit arranged to be actuated by said float arm and including a single switch casing, a lever pivoted thereto for movement substantially in the plane in which said float arm moves and includin a yoke section receiving the outer end of said float arm and a pair of co-planar contact-actuating lever sections positioned one above the other, a first pair of switch contacts disposed in said casing and arranged to be controlled by one of said lever sections, and a second pair of switch contacts also disposed in said casing and arranged to be controlled by the other lever section as the lever is moved about its pivot on the switch casing by the movement of said float arm.

3. In a liquid level responsive device, a float chamber, a float mounted therein and having a float arm sealingly pivoted to and extending outwardly of said chamber, and a control device carried by said chamber and including a single casing, a lever pivoted thereto for movement substantially in the plane in which said float arm moves and having a recess receiving the extended end of said float arm, whereby movement of said float in swinging said arm pivots said lever, and a pair of switch units both disposed within said casing and each having a plunger extending outwardly thereof and into engagement with said lever on opposite sides of said pivot, whereby oscillations of said lever in response to movements of the float control said switch units, said plungers being co-planar and positioned one above the other.

OSCAR F. CARLSON. 

